The present proposal is concerned chiefly with defining the contribution of the 2 intestinal lecithin synthetic pathways which might be expected to provide the lecithin associated with intestinal lipoprotein formation and specifically that associated with chylomicrons. The first pathway, which is dependent on lysolecithin acyltransferase, will be evaluated in rats who have a duodenal cannula, a bile duct cannula and a cannula in the intestinal lymphatic. These rats will be infused through the duodenal cannula with triolein dispersed as an emulsion, varying amounts of lecithin and (C14 glycerol) lecithin. The contribution of infused lecithin to chylomicron lecithin will be determined by comparing the specific activity of the lecithin infused to the specific activity of chylomicron lecithin. The second source of lecithin for this pathway is blood which will be evaluated in rats prepared and infused as above (without C14 lecithin) plus a femoral vein catheter through which (C14 glycerol) lysolecithin will be infused. The contribution of chylomicron lecithin synthesis by the second (cholinephospho-transferase dependent) pathway will be evaluated in rats prepared with cannulae and infused as before with the radiolabel P32 or C14 choline. The relative lecithin specific activities will be utilized to calculate the chylomicron lecithin derived via this pathway as before.